1. Field of the Invention
The invention relates to a method for measuring fluid levels in a reservoir. More particularly, the invention relates to a method for measuring fluid levels in a reservoir having multiple fluids being stored therein by analyzing the resonance of the output signal of the fluid level sensing assembly.
2. Description of the Related Art
The storage and delivery of liquids is an important feature of many mechanisms. In an automotive environment, proper delivery of liquids is essential for the functioning and maintenance of a motor vehicle. By way of example, a motor vehicle will not function without fuel, typically liquid gasoline. That same motor vehicle will not function properly without the proper amount of oil stored in the internal combustion engine allowing it to lubricate and cool itself. These are just two fluids in a particular environment that require close observation to make sure its host mechanism, i.e., the motor vehicle, can operate properly.
Currently, there are a number of ways in which a fluid level may be measured. The mechanisms used to measure the fluid level help determine if more fluid is required in order to continue the proper maintenance and operation of the host mechanism. Fluid level measuring mechanisms include floating arm mechanisms, pressure sensors, capacitive sensors, and ultrasonic sensors. The most commonly used fluid level measuring system is the floating arm mechanism.
The floating arm mechanism is an imperfect mechanism for several reasons. First, the floating arm mechanism requires moving parts inside a liquid-filled container. This requires increased time to install the floating arm mechanism and seal it and the container or reservoir. Resistive strips used by the floating arm mechanism are susceptible to contamination and can develop contact problems. The contamination and contact problems result in erroneous measurements. Looking forward, the floating arm fluid measuring mechanism will not be able to differentiate between different types of liquids within the same reservoir. This problem will increase in the automotive environment as different types of fuels will be accepted by each motor vehicle resulting in the stratification of the fluids within a particular reservoir.
Another reason the floating arm mechanisms are inferior is that they measure liquid levels inefficiently when the reservoir holding the liquid is unusually shaped. Oftentimes when a motor vehicle is an all-wheel drive vehicle, an extra drive shaft is required to extend along the underbody of the motor vehicle. The extra shaft typically extends through the space used by the fuel tank. Therefore, the fuel tank must be modified resulting in an unusually shaped fuel tank. Multiple floating arm mechanisms are required to get accurate readings from these unusually shaped fuel tanks. This adds considerable costs to the fuel tank construction.
Compounding the problem of measuring liquids in a reservoir is the fact that liquids can separate into multiple phases wherein the various phases do not mix and physically separate. This typically occurs when the liquid in the reservoir is contaminated. Readings taken from level sensors will be inaccurate if they cannot adequately differentiate between the differing phases.
In some situations, the liquids may be compound liquids by design. More specifically, new forms of gasoline include gasoline/alcohol mixtures. These types of fuels can easily separate or stratify because they are more susceptible to absorbing water.